1. A. B. Govorkov, Teor. Matem. Fiz., 41, 318 (1979).
2. A. B. Govorkov, J. Phys. A, 13, 1673 (1980).
3. A. B. Govorkov, Fiz. Elem. Chast. Atom. Yadra, 14, No. 56, 1229 (1983).
4. T. D. Palev, Preprint of Joint Institute for Nuclear Research E17-10550 (1977).
5. T. D. Palev, Rep. Math. Phys., 18, 117; 129 (1980).